It has been a rather long time since we reviewed what a student can learn from assembling a small, direct current (DC) motor in a classroom or home school setting. This post does not include the simple DC motor known as the Beakman’s motor. The Beakman’s motor is a very simple motor that does show an interaction between a magnet and an energized coil, but it does not have material (such as an iron armature) inside the coil to improve performance of the motor. Also, with the wobbling in its “cradle” it shows it is not a precision built piece of equipment. However, despite these misgivings some of the basic principles are able to be taught and learned (see Figure 1).
Here are few concepts that would be good to integrate in any discussion about DC motors:
- A key tenet of a motor is magnetism. It is a force that attracts and repels. A magnet has a magnetic pole at each end. One is called the north (N) and the other end is called the south (S) pole.
- Like poles repel, e.g., a N-end of one magnet will push away from the N-end of another magnet. Opposite poles attract such that one N-pole of one magnet will pull toward the S-pole of a different magnet.
- The Earth is a giant magnet that has a north and south magnetic pole. The poles seem to wander but it happens very slowly so compasses are able to help in navigation.
- An electromagnet is made by wrapping a wire that carries an electric current around an iron bar. This ends up being a magnet that can be turned on and off at will.
- An electric motor uses the attracting and repelling properties of magnets to create motion. An electric motor contains two magnets. A permanent magnet (also called a fixed magnet that does not spin) and a temporary magnet. The temporary magnet is a special type of magnet mentioned above, it is called an electromagnet.
- The permanent magnet has a magnetic field all the time but the electromagnet only has a magnetic field when current is flowing through the wire.
These are the main concepts necessary to have a student understand the background of a small, DC motor. In future blogs, we will talk about applications of this type of motor.
Quote for the Day: “If you cannot do great things, do small things in a great way.” — Napoleon Hill